Create new src/common/state_control.[ch] to define state control functions.

Different clients provide similar functionality such as scontrol and sview.
These new files are intended to hold common functions that can be used by
these clients. This will help to avoid behavior divergence across them and
stop duplicating code.

src/common/Makefile.am libcommon_la_SOURCES have been modified accordingly,
and a following autogen.sh execution should be committed right after to
reflect the changes in the generated src/common/Makefile.in file.

Bug 2329